Polypropylene resin composition and gas permeable film using the same

Abstract

Provided are a novel polypropylene resin composition, a gas permeable film comprising the same and provided with satisfactory optical characteristics (transparency, gloss and see throughness) as well as an excellent gas permeability (water vapor, oxygen and ethylene gas) without damaging a rigidity and a vegetable and fruit freshness long term-maintaining method using the above gas permeable film for a wrapping film. The polypropylene resin composition described above comprises 40 to 95% by weight of a propylene polymer (A) and 5 to 60% by weight of an ethylene / propylene / butene random copolymer (B) having a butene content of 3 to 40% by weight and an ethylene content of 10 to 30% by weight, wherein a ratio (etaB / etaA) of an intrinsic viscosity etaB of the component (B) described above to an intrinsic viscosity etaA of the component (A) described above falls in a range of 0.5 to 1.3; and the etaB described above falls in a range of 0.5 to 3.0 dl / g. The gas permeable film described above is a single layer or multilayer film comprising at least one layer of a film of the polypropylene resin composition described above and having a thickness of 10 to 100 mum, and it has the following characteristics: (1) a permeability TH2O of water vapor is 9 to 50 g / m2.24 h (based on JIS Z 0208), (2) a permeability TO2 of oxygen is 600 to 12500 nmol / m2.s.100 kPa (based on JIS K 7126-A) and (3) a permeability Tethylene of ethylene gas is 600 to 22500 nmol / m2.s.100 kPa (based on JIS K 7126-A).

Description

[0001] This application claims the priority benefit of Japanese application serial No. 2001-104626, filed Apr. 3, 2001.BACKGROUND OF THE VENTION[0002] 1. Field of the Invention[0003] The present invention relates to a novel polypropylene resin composition, a gas permeable film comprising the same and provided with satisfactory optical characteristics (transparency, gloss and see throughness) as well as an excellent gas permeability (water vapor, oxygen and ethylene gas) without damaging a rigidity and a method for maintaining a freshness of vegetables and fruits over a long period of time using the above gas permeable film for a wrapping film.[0004] 2. Description of the Related Art[0005] A polypropylene film has a rigidity and excellent optical characteristics (transparency, gloss and the like) which are required to packaging materials and therefore has widely been used. However, when a polypropylene film is used as a wrapping material for vegetables and fruits, it does not have a ...

AI Technical Summary

Benefits of technology

[0019] The polypropylene resin composition of the present invention is characterized by containing a propylene homopolymer as the component (A). The propylene homopolymer contained therein makes it possible to maintain a rigidity of the resulting gas permeable film.

[0035] Further, the gas permeable film according to the present invention is, as explained above, excellent in a transparency and particularly a see throughness which are optical characteristics, and it has an excellent film strength and fuse sealing property even in a single layer structure. Further, controlling of a content of the component (B) and a thickness of the film makes it possible to control a permeability of gas and provides the polypropylene film for wrapping vegetables and fruits with very suited performances.

[0063] The vegetable and fruit freshness long term-maintaining method in the present invention is characterized by using the gas permeable film according to the present invention as a film for wrapping vegetables and fruits. Accordingly, the gas permeable film explained above according to the present invention endowed with excellent gas permeability and optical characteristics in combination can maintain a freshness of vegetables and fruits wrapped therewith over a long period of time.

[0066] Use of a vegetable and fruit wrapping material comprising an impact-cushioning member (for example, foamed styrol trays, foamed propylene trays and the like) and the gas permeable film of the present invention makes it possible not only to obtain a freshness-maintaining effect by virtue of the characteristics of the gas permeable film of the present invention but also protect the vegetables and fruits from impact, which results in making it possible to prevent the vegetables and fruits from being damaged and maintain a freshness thereof over a longer time of period. For example, when a peach is wrapped with a vegetable and fruit wrapping material prepared by combining the gas permeable film of the present invention with a foamed styrol-made pan, the peach is protected from impact by the foamed styrol-made pan and less liable to be damaged. Further, the partial presence of the gas permeable film of the present invention allows a freshness-maintaining effect to be exhibited by virtue of the gas permeability thereof, and further provided as well is the effect that the excellent see throughness and transparency thereof make it easy to visually confirm the state of the peach which is a wrapped article.EXAMPLES

Problems solved by technology

However, when a polypropylene film is used as a wrapping material for vegetables and fruits, it does not have a satisfactory gas permeability against water vapor, oxygen and ethylene gas, and therefore it has been used making holes for permeating gas.

However, water vapor can not be prevented from vaporizing from vegetables and fruits, so that there has been the problem that vegetables and fruits are liable to be dried and freshness thereof is lost

Known is a film which shows a gas permeability without carrying out such drilling work and can maintain a freshness of vegetables and fruits (International Publication WO99 / 51665), but there has been the problem that the film does not have satisfactory transparency, gloss and see throughness (hereinafter referred to as .left brkt-top.optical characteristics.right brkt-bot.) which are required in an actual distribution route.

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